1. Field of the Invention
This invention pertains generally to implements or apparatus for applying pushing or pulling force, and more particularly to an improved boat lift used to raise boats from a body of water and subsequently lower them back into the water.
2. Description of the Related Art
Owners of waterfront properties, resort owners, and other persons who regularly access or provide access to bodies of water must store marine craft. Most preferably, this storage is as convenient as possible, and as close and readily accessible to the shoreline as possible. Frequently, docks, piers or the like are provided that extend into the water body from the actual shoreline, above water level to permit dry passage, and that extend a distance sufficient to reach a water depth adequate for safe passage of marine craft. When the water craft are repetitively used, they may be left adjacent the dock or secured thereto, and are consequently available for immediate use. Unfortunately, the vagaries of weather frequently require the water craft to be removed, such as when a severe storm approaches, or when the body of water might freeze. Additionally, minor servicing,  painting, hull inspections and the like will also necessitate the removal of the water craft from the water.
Some persons prefer to launch the water craft from trailer and then return the water craft to the trailer. By removing the water craft from the water, no further efforts need to be made to prepare for storms and the like. Unfortunately, to reasonably unload and reload the water craft from trailer generally requires a significant amount of time, available landing access, storage space for vehicle and trailer, and also generally requires more than one person. Additionally, the use of a trailer all too frequently results in the water craft being accidentally damaged just in the loading and unloading operations. Consequently, the water craft is not readily available for use, and may require multiple persons to ready the water craft for use.
To provide more convenient storage and use of the water craft, and reduce the risks of damage or the need to remove the water craft in the event of adverse weather or the like, boat lifts have been designed that may be placed within the water adjacent the dock. Alternatively, these lifts may include attachment directly to the dock. To enable the water craft, which may typically be a motor boat, personal water craft, or the like, though not strictly limited thereto, to be raised or lowered, the boat lift will typically comprise an operator for power input, whether manual or motorized, a gearing arrangement, some type of safety system, whether a ratcheting system or some other equivalent means, and a boat support such as a custom hull support or suitable adjustable or universal boat support. In the case of manual systems, a large wheel is frequently provided, typically several feet in diameter, which may be easily handled and operated by most persons.
The safety system is necessitated by the weight of the water craft, and the possibility for damage to the water craft or injury to persons in the event the water craft is undesirably released in  an uncontrolled manner. Unfortunately, ratchet systems tend to be relatively large, somewhat cumbersome, extremely noisy, and exposed gears may in and of themselves present a safety hazard.
As an alternative, motorized systems have been proposed that combine motor with worm gear transmission system. The resistance of the motor, which is further magnified through the worm gear, is adequate to prevent the lift from running away and the water craft from undesirably falling. Exemplary of such system is U.S. Pat. No. 6,021,692 to Norfolk et al, the teachings which are incorporated herein by reference. Nevertheless, and acknowledged in the Norfolk et al patent, the use of electric motors is disadvantageous in many applications. The environment within which these motors must be operated is frequently harsh, and often leads to early failure. As such, the reliability of a motorized system suffers. Furthermore, not all locations will have ready access to power, particularly near the water. Finally, the system as a whole cannot be designed to operate as reliably as a manual system, and maintenance takes time away from the primary activity, boating.